Cold Season 500 hPa Cutoff Cyclone Precipitation Distribution

and a Case Study

Tony FracassoDepartment of Earth and Atmospheric Sciences

University at Albany, State University of New York

Advisors: Lance Bosart and Dan Keyser

NWS Focal Point: Mike Evans (Binghamton, NY)

Project Objectives

a) Stratify precip. distribution relative to cutoff cyclone tracks as identified in composites developed by B. Smith (2003)

b) Map/understand cutoff cyclone precipitation characteristics in composites

c) Document mesoscale precipitation signatures in case studies representative of each of the composites

Project Objectives, cont.

d) Document contribution of upright and slantwise ascent to precipitation in case studies representative of each of the composites

e) Revisit D. Novak (2002) findings on bands/frontogenesis through selectedcase studies

Cool season composite mean cutoff cyclone tracks

B. Smith (2003)

Progress to date

• Monthly composites of precipitation where a 500 hPa low was present

• Graphical and textual record of cool season (October – May) 500 hPa cutoff low tracks (1980-1998)– Both sets of tracks are in agreement

Outer Domain

in./daymm/day

NOV

MAYMAR

JAN

1980-1998

1980-1998

Progress to Date: Case Studies

• Detailed first pass on 23-30 May 2003 cutoff• Preliminary information on other case studies

– Christmas snowstorm (25-26 Dec. 2002)

– 3-4 January 2003 snowstorm

– 7 February 2003 snowband near Boston

– Presidents’ Day snowstorm (16-17 Feb. 2003)

– 10-14 May 2003 cutoff

Current Work

• Categorizing cutoffs by individual track– Ex: 11 “Mid-Atlantic Track” cutoffs during

Octobers 1980-1998 (total of 25 days)

• Use simple composite and storm-relative compositing methods

• Build a user-friendly database of cutoffs (1980-1998)

in./day

mm/day

in./day

mm/day

All tracks Octobers 1948-1998

Mid-Atlantic tracks Octobers 1980-1998

Maximum surface report:

13.19 in. (335.0 mm) at

Greenland, NH (Rockingham

County)19

23

22

21

20

Accumulated Precipitation (cm) (24 – 29 May 2003)

Dates are 12Z locations

00Z 24 May 2003 – 500 hPa Heights (dam) and Abs. Vorticity (x10-5 s-1)

12Z 24 May 2003

00Z 25 May 2003

12Z 25 May 2003

00Z 26 May 2003

12Z 26 May 2003

00Z 27 May 2003

12Z 27 May 2003

12Z 26

12Z 27

00Z 28 May 2003

12Z 28 May 2003

12Z 27

12Z 28

00Z 29 May 2003

12Z 29 May 2003

12Z 28

12Z 29

U.S. Radar loop 00Z 23– 23Z 29 May 2003

Future Work

• Analyze precip. patterns between cutoffs of the same track

• Examine the other cases more closely (synoptic scale and mesoscale)

• Attempt to find a forecasting “heads-up” for cutoff precip.

Banding to beat the snow…